He said despite Australia's involvement in Vietnam being "perhaps the most divisive and destructive in Australian society since the events leading up to the Eureka Stockade" it had an important legacy.

You've fought an enormous fight over the years... -
Ken Bowen

"There evolved a real benefit for Australia in that for the first time our government listened to the people... the government heard their voice and acted and brought us home," he said.

Another was the recognition of post-traumatic stress disorder as a legal condition, Mr Bowen said.

"Not only has that condition been recognised and extensively researched, Australia now has world-recognised treatment programs available to those affected," he said.

"Indeed, those programs are not only available to ex-servicemen and women but to our police forces, our ambulance people, our firemen, any of our emergency services who go about their day-to-day lives and encounter trauma."

He ended the service with a message to Vietnam veterans.

"You've fought an enormous fight over the years, not just in Vietnam but subsequently and I personally believe, to quote a phrase, you've all done very well," he said.